In recent years, there is proposed a technology in which a power generation device for performing an independent power generation through the use of natural energy source is installed in a house and in which an electric power generated by the power generation device is supplied to various kinds of electric appliances such as an illumination device and the like (see Patent document 1). In Patent document 1, a solar cell and a battery storing the electric power generated in the solar cell are installed in a house.
If an electric power is available from a main power supply represented by a commercial power source, the electric power is supplied from the main power source to various kinds of electric appliances. At this time, the AC power supplied from the main power source is converted to a DC voltage which in turn is supplied to electric appliances (often referred to as “DC appliances”) driven by the DC voltage. On the other hand, if the electric power is not available from the main power source due to a power outage, the DC appliances are operated by the DC power supplied from a battery.
In the event that a power outage occurs in an apartment building having a plurality of dwelling units, the DC power is supplied from the battery to the respective dwelling units.
Patent document 1: Japanese Patent Application Publication No. 2009-159780
In the power distribution system disclosed in Patent document 1, the DC power charged in the battery is used when the house suffers from a power outage. In recent years, however, a strong demand exists to effectively use the DC power charged in a battery, thereby reducing the use amount of the AC power supplied from a main power source to a house.